As wireless systems continue to evolve, communications between a mobile switching center (MSC) and its base stations are moving to an Internet Protocol (IP) based transport mechanism. (As used herein, the term wireless systems refers to e.g., CDMA (code division multiple access), GSM (Global System for Mobile Communications), the proposed UMTS (Universal Mobile Telecommunications System), etc.) Given the nature of wireless communications, e.g., real-time voice, any IP-based transport needs to utilize a protocol that accommodates real-time applications.
One such protocol is the Real Time Protocol (RTP) (e.g., see H. Schulzrinne, R. Frederick, V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications,” RFC 1889). RTP is attractive since it is an available Internet Engineering Task Force (IETF) protocol for handling real-time streams. RTP traffic is encapsulated in UDP (user datagram protocol), and IP packets.
Unfortunately, the use of RTP/UDP/IP generates a large overhead when voiceover-IP applications are run over wireless networks since the voice payload is usually small (e.g. 10 to 20 bytes) while the RTP/UDP/IP header is 40 bytes.